Band Strengths Research Articles

Infrared spectra of complex organic molecules in astronomically relevant ice mixtures

Context. The increasing sensitivity and resolution of ground-based telescopes have enabled the detection of gas-phase complex organic molecules (COMs) across a variety of environments. Many of the detected species are expected to form on the icy surface of interstellar grains and transfer later into the gas phase. Therefore, icy material is regarded as a primordial source of complex molecules in the interstellar medium. Upcoming James Webb Space Telescope (JWST) observations of interstellar ices in star-forming regions will reveal infrared (IR) features of frozen molecules with unprecedented resolution and sensitivity. To identify COM features in the JWST data, laboratory IR spectra of ices for conditions that simulate interstellar environments are needed. Aims. This work provides laboratory mid-IR spectra of methyl cyanide (CH3CN, also known as acetonitrile) ice in its pure form and mixed with known interstellar molecules at cryogenic temperatures. The spectroscopic data presented in this work will support the interpretation of JWST ice observations and are made available to the community through the Leiden Ice Database for Astrochemistry (LIDA). Methods. Fourier transform IR spectroscopy is used to record the mid-IR spectra (500–4000 cm−1/20–2.5 µm, with a resolution of 1 cm−1 ) of methyl cyanide (acetonitrile, CH3 CN) mixed with H2O, CO, CO2, CH4, NH3, H2O:CO2, and H2O:CH4:NH3, at temperatures ranging from 15 to 150 K. The refractive index (at 632.8 nm) of pure amorphous CH3CN ice at 15 K and the band strength of selected IR transitions are also measured. Results. We present a variety of reference mid-IR spectra of frozen CH3CN that can be compared to astronomical ice observations. The peak position and full width at half maximum (FWHM) of six absorption bands of frozen methyl cyanide in its pure form and mixed ices, at temperatures between 15–150 K, are characterized. These bands are the following: the CH3 symmetric stretching at 2940.9 cm−1 (3.400 µm), the CN stretching at 2252.2 cm−1 (4.440 µm), a peak resulting from a combination of different vibrational modes at 1448.3 cm−1 (6.905 µm), the CH3 antisymmetric deformation at 1410 cm−1 (7.092 µm), the CH3 symmetric deformation at 1374.5 cm−1 (7.275 um), and the CH3 rock vibration at 1041.6 cm−1 (9.600 um). Additionally, the apparent band strength of these vibrational modes in mixed ices is derived. The laboratory spectra of CH3CN are compared to observations of interstellar ices toward W33A and three low-mass Young Stellar Objects (YSO). Since an unambiguous identification of solid methyl cyanide toward these objects is not possible, upper limits for the CH3CN column density are determined as ≤2.4 × 1017 molecules cm−2 for W33A and 5.2 × 1016, 1.9 × 1017, and 3.8 × 1016 molecules cm−2 for EC92, IRAS 03235, and L1455 IRS3, respectively. With respect to solid H2O, these values correspond to relative abundances of 1.9, 3.1, 1.3, and 4.1%, for W33A, EC92, IRAS 03235, and L1455 IRS3, respectively.

Mayo 2A Olecranon Kırık Tespitinde K-teli veya Kanüllü Vida ile Uygulanan Gergi Bantlama Metodunun Karşılaştırması: Biyomekanik Çalışma

Aim: The study aimed to compare the biomechanical stability and strength of the tension band wiring method used to treat mayo 2A olecranon fractures with Kirschner (K)-wire or cannulated screw configurations. Material and Methods: A total of 24 anatomical ulna models (Sawbones Model 1004, Pacific Research Laboratories, Vashon Island, WA) used in the study were divided into two equal groups of 12, tension band fixation with K-wire (Group 1) and tension band fixation with cannulated screw (Group 2), and groups were compared. The mechanical comparison was performed with a universal measuring machine (Shimadzu Autograph 50 kN; Shimadzu Corp). Results: Fixation methods comparison (K-wire/cannulated screw) were the main factors that determined the stability and the strength of the internal fixation. The median flexion strength of Group 1 was 107.92 (range, 94.22-121.72) N, and that of Group 2 was 109.67 (range, 105.07-113.86) N. The median varus strength of Group 1 was 100.02 (range, 83.24-102.18) N, and that of Group 2 was 76.32 (range, 68.44-78.43) N. Varus strength and stiffness were significantly higher in the K-wire group than in the cannulated screw group (both p values were <0.001). No significant differences were detected between the groups regarding flexion strength and stiffness (both p values were 0.999). Conclusion: Although no significant differences were detected between the two fixations in flexion bending cyclic loading, a significantly more stable fixation was achieved in tension banding applied with K-wire in varus bending cyclic loading. No reduction loss was detected during cyclic loading tests in either technique.

Early identification of high-risk individuals for monoclonal antibody therapy and prophylaxis is feasible by SARS-CoV-2 anti-spike antibody specific lateral flow assay

Monoclonal antibody therapy has been approved for prophylaxis and treatment of severe COVID-19 infection. Greatest benefit appears limited to those yet to mount an effective immune response from natural infection or vaccination, but concern exists around ability to make timely assessment of immune status of community-based patients where laboratory-based serodiagnostics predominate. Participants were invited to undergo paired laboratory-based (Abbott Architect SARS-CoV-2 IgG Quant II chemiluminescent microparticle immunoassay) and lateral flow assays (LFA; a split SARS-CoV-2 IgM/IgG and total antibody test) able to detect SARS-CoV-2 anti-spike antibodies. LFA band strength was compared with CMIA titer by log-linear regression. Two hundred individuals (median age 43.5 years, IQR 30−59; 60.5% female) underwent testing, with a further 100 control sera tested. Both LFA band strengths correlated strongly with CMIA antibody titers (P < 0.001). LFAs have the potential to assist in early identification of seronegative patients who may demonstrate the greatest benefit from monoclonal antibody treatment.

Infrared intensities of methyl acetate, an interstellar compound - comparisons of three organic esters

The mid-infrared (IR) spectra of the simplest aliphatic esters have been studied in the past in the solid, liquid, and gas phases with an emphasis on vibrational frequencies and peak assignments. However, relatively little has been published on the IR intensities of the amorphous forms of these compounds. These IR intensities are of particular interest to the astrochemical community as they are needed to help quantify laboratory measurements of the formation and destruction of extraterrestrial molecules, including esters. Here we report and compare IR intensities of three organic esters: methyl formate, methyl acetate, and methyl propionate, all studied with the same equipment and procedures. Of these three esters, our main interest is with methyl acetate, for which little quantitative IR work is available. For each ester, we report apparent absorption coefficients and band strengths, and compare them to earlier work. We also have calculated the first IR optical constants for both amorphous and crystalline methyl acetate. We use our new results to measure vapor pressures and a sublimation enthalpy for methyl acetate and to comment on a radiation-chemical experiment with methyl acetate and how it can be better quantified.

The Spectral Properties of Pitted Impact Deposits on Vesta as Seen by the Dawn VIR Instrument

Pitted impact deposits (PIDs) on Vesta have been shown to exhibit distinct spectral characteristics with respect to their surrounding host deposits and other typical Vestan areas regarding the first major pyroxene absorption near 0.9 μm. The PIDs, especially those in the ejecta blanket of the large crater Marcia, show higher reflectance and pyroxene band strength with respect to their impact deposit surroundings. This study complements the spectral characterization of the PIDs on Vesta with Visible and Infrared Spectrometer observations obtained by NASA’s Dawn mission. In particular, we focus on the second major pyroxene absorption near 1.9 μm. We analyze nine PIDs in the ejecta blanket of the crater Marcia, as well as PIDs within the crater-fill deposits of the craters Marcia, Cornelia, and Licinia. We find that the second pyroxene absorption behaves in similar ways as the first major pyroxene absorption. The PIDs in Marcia’s ejecta blanket show higher reflectance and pyroxene band strength with respect to their immediate impact deposit surroundings. The PIDs present in the crater-fill deposits of Marcia, Cornelia, and Licinia, however, do not show such spectral characteristics. This is also consistent with previous observations of the first pyroxene absorption band. Based on the experimental results of other studies, we speculate that the observed spectral distinctness arises from an oxidation process in the interior of impact deposits, where Fe cations migrate within their host pyroxene grains. Thus, the surfaces of (melt-bearing) impact deposits might be different from their interiors, apart from space-weathering effects.

Variability of Hydration Across the Southern Hemisphere of the Moon as Observed by Deep Impact

AbstractMeasurements of the 3 μm absorption feature, associated with the presence of hydroxyl and potentially molecular water, were first observed in 2009 by three separate spacecraft’ observations. Subsequent observations have revealed widespread but variable hydration over the sunlit regions of the Moon. The variability can help to disentangle the individual contributions of OH and H2O to the 3 μm absorption feature and provide insight into the mechanism of production and loss of OH/H2O on the lunar surface. We investigate the spatial and diurnal variations of hydration on the southern hemisphere of the Moon as observed by the Deep Impact spacecraft during the lunar flybys in 2009 at spatial scales of 30–70 km/pixel. For a subset of observations of across the lunar south polar region (∼2% of the lunar surface), repeat coverage includes three different times spanning half a lunar day, allowing for exploration of diurnal variability. We determine that OH/H2O is widespread but variable across the lunar south pole. At all but the lowest temperatures observed, highland regions have stronger hydration absorption features than the maria. Changes in band strength demonstrate variable loss rates controlled by surface temperatures with H2O lost quicker at higher temperatures. Observed variability in the band shape strongly suggests higher H2O abundance at low temperatures. These observations are strong evidence that the unique shape of the 3 μm band is due to both OH and H2O. The rapid diurnal evolution of the absorption feature implies that migration of these constituents occurs locally over short distances driven by temperature changes.

Large deformation slope failure — A perspective from multiscale modelling

Slope failure analysis is a traditional topic in geotechnical engineering. Current continuum modelling with phenomenological constitutive models fails to capture the physical mechanism at the particle scale. Discrete numerical methods may well describe particle scale features but are limited by the computational cost to handle practical engineering problems. In this paper, a coupled MPM/DEM hierarchical multiscale model is developed and implemented for slope failure analysis, aiming to obtain a comprehensive understanding of the slope failure and post-failure behaviours. For improving the numerical stability, the standard MPM version is modified by incorporating the Affine-particle-in-cell (APIC) velocity update format and B-spline basic function. A represent volume element (RVE) replacement approach is proposed in solving the excessive deformation problem during the slope failure simulation. Both the dynamic failure processes of cohesive and non-cohesive soil slopes are investigated. It is found that for non-cohesive soil slopes, the stability is mainly controlled by the microscopic frictional property and gradation, while the post-failure stage is dominated by particle level friction. For cohesive soil slopes, Johnson–Kendall–Robert (JKR) cohesive model is adopted in representing adhesive effect between particles. The results show that the slope failure pattern transmits from collapse to shear failure with increasing surface energy density. By statistical analysis on the attractive force between particles, the strength of the shear band is found to be controlled by cohesive effect for the top part and frictional property for medium and bottom parts.

Robust Testing for Bollinger Band, Moving Average and Relative Strength Index

We test whether the moving average indicator is profitable in trend following and compare the result with common momentum indicators such as Relative Strength Index (RSI) and Bollinger Band (BB). Our sample runs from January 1, 1963, through December 31. 2019. We test whether the signals generated are profitable and compare their success in timing the portfolios based on the previous year's volatility using the Center for Research in Security Prices (CRSP) data. We note the portfolios sorted by volatility to be trend following and use common entry points for timing them. We find all indicators to be more profitable than the Buy and Hold (BH). The moving average (MA) has the strongest return, while BB and RSI show positive return they do worse than the MA. The results hold across all portfolio deciles sorted by both size and volatility. The indicators for RSI and BB are robust to other specifications for entry and parameters. We also show price level analysis for both RSI and BB as well as a trailing three year analysis for the volatility deciles and moving average.

Laboratory Measurements of Stretching Band Strengths of Deuterated Quenched Carbonaceous Composites

The observed large variation in the abundance of deuterium (D) in the interstellar medium suggests that a significant fraction of D may be depleted into polycyclic aromatic hydrocarbons (PAHs). Signatures of the deuteration of PAHs are expected to appear most clearly through the C–D stretching modes at 4.4–4.7 μm, whose strengths in emission spectra relative to those of the C–H stretching modes at 3.3–3.5 μm provide the relative abundance of D to hydrogen (H) in PAHs, once we have accurate relative band strengths of both stretching modes. We report experimental results of the band strengths of the C–D stretching modes relative to the C–H stretching modes. We employ a laboratory analog of interstellar carbonaceous dust, Quenched Carbonaceous Composite (QCC), and synthesize deuterated QCC (D-QCC) by replacing the QCC starting gas of CH4 with mixtures of CH4 and CD4 with various ratios. Infrared spectra of D-QCC are taken to estimate the relative band strengths of the stretching modes, while the D/H ratios in the D-QCC samples are measured with a nanoscale secondary ion mass spectrometer. We obtain relative strengths of aromatic and aliphatic C–D to C–H stretches as 0.56 ± 0.04 and 0.38 ± 0.01 per D/H, respectively. The ratio for the aromatic stretches is in good agreement with the results of theoretical calculations, while that for the aliphatic stretches is smaller than that for the aromatic stretches. The present results do not significantly change the D/H ratios in interstellar PAHs that have previously been estimated from observed spectra.

Effect of Graphene/Spherical Graphite Ratio on the Properties of PLA/TPU Composites.

Wave-absorbing materials are developing in the direction of “light weight, wide frequency band, thin layer and high strength”, and it is difficult to achieve the synergy between wave-absorbing performance and mechanical properties when graphene absorbent is compounded with a single resin matrix. In this paper, based on the preparation of a new composite absorbing wire with a graphene (GR)/spherical graphite (SG) double absorbent and polylactic acid (PLA)/thermoplastic polyurethane (TPU) double matrix, we proposed a new method to prepare samples for testing the electromagnetic parameters and tensile strength by fused deposition modeling (FDM). Furthermore, the effect of SG/GR ratio on the microwave absorbing properties and mechanical properties of PLA/TPU composites was specifically studied. It was found that when the ratio of SG/GR was small (0:5, 1:4), the dielectric loss (interfacial polarization loss, dipole polarization loss, conductivity loss) and attenuation ability of the composites were stronger, and the impedance matching was better. When the SG/GR ratio was large (5:0, 4:1), the composites had high strength and toughness. When the ratio of SG/GR was moderate (2:3, 3:2), it could retain the absorbing and mechanical properties of the absorbing materials. On the one hand, the SG and PLA/TPU matrix formed an “island structure”, which improves the dispersion of GR; on the other hand, the GR and PLA/TPU matrix formed a “core-shell structure”, which promotes polarization and multiple scattering.

Infrared spectra of benzene ices: Reexamination and comparison of two recent papers and the literature

Infrared spectroscopic results on benzene (C6H6) ices from two recent papers, one published here, are compared to each other and to literature results from 60 years ago. Qualitative and quantitative differences are described, partly in terms of spectral resolution, and errors in one paper are identified that, once corrected, could bring the two recent publications into agreement with each other. A solution is provided for an unexplained disagreement with the literature noted by the authors of one paper. It is concluded that the only accurate, extensive set of IR absorption coefficients, band strengths, and optical constants now available for amorphous and crystalline benzene are those recently published here by the author and a colleague. Suggestions are made for future work to change this situation.

Alteration of collagen thermal denaturation, structural and the abrogation of allergenicity in eel skin induced by ohmic heating

This study aimed to evaluate the effect of ohmic heating (OH) on the thermal denaturation, structure, and allergenicity of collagen in fresh eel skin. The allergenicity of collagen decreased by approximately 70% at 50 °C as measured by simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and ELISA in vitro. SDS-PAGE analysis showed that the molecular weight of collagen did not decrease, but the band strength decreased with an increase in the processing temperature. FTIR and SEM analyses showed that the secondary structure and microstructure of collagen also changed. The water retention, dielectric properties and amino acid content of collagen also decreased with increasing temperature. Compared to water bath heating (WH), OH required significantly less time and energy and reduced the allergenicity of fish skin collagen through protein unfolding and secondary structure changes, thus potentially reducing the allergenicity of eel.

Emu: a case study for TDI-like imaging for infrared observation from space

A wide-field zenith-looking telescope operating in a mode similar to time-delay-integration (TDI) or drift scan imaging can perform an infrared sky survey without active pointing control, but it requires a high-speed, low-noise infrared detector. Operating from a hosted payload platform on the International Space Station (ISS), the Emu space telescope employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array to provide powerful new observations of cool stars at the critical water absorption wavelength (1.4 μm) largely inaccessible to ground-based telescopes due to the Earth’s own atmosphere. Cool stars, especially those of spectral-type M, are important probes across contemporary astrophysics, from the formation history of the Galaxy to the formation of rocky exoplanets. Main sequence M-dwarf stars are the most abundant stars in the Galaxy and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey will deliver critical stellar properties of these cool stars by inferring oxygen abundances via measurement of the water absorption band strength at 1.4 μm. Here, we present the TDI-like imaging capability of Emu mission, its science objectives, instrument details, and simulation results.

A fundamental assessment of the concept of mean beam length for application for multi-dimensional non-gray radiative heat transfer

The traditional concept of mean beam length (MBL) and its recommended empirical expression is demonstrated to be inaccurate for general application for the evaluation of multi-dimensional non-gray radiative heat transfer. A new concept, namely Point Mean Beam Length (PMBL), is proposed and the formulation of PMBL is provided. The mathematical properties of PMBL for three common geometries including sphere, cylinder, and slab are presented. Results show that PMBL is more effective in generating an accurate evaluation of radiative heat transfer from a differential area to any finite area at the boundary of an enclosure with an isothermal absorbing/emitting medium. The deficiency of the traditional mean beam length empirical expression is illustrated. A concept of “optimal” point mean beam length (OPMBL) is demonstrated to be a more accurate length scale for practical applications. In contrast to the traditional MBL, a single value of OPMBL is applicable for all gas absorption bands, independent of the strength and shape of the absorption bands. The proposed work provides a mathematically validated approach to efficiently and accurately evaluate the radiation heat transfer within an isothermal, non-gray, multi-dimensional medium.

Ultracool dwarfs observed with the Spitzer infrared spectrograph – II. Emergence and sedimentation of silicate clouds in L dwarfs, and analysis of the full M5–T9 field dwarf spectroscopic sample

ABSTRACT We present a uniform analysis of all mid-infrared R ≈ 90 spectra of field M5–T9 dwarfs obtained with the Spitzer Infrared Spectrograph (IRS). The sample contains 113 spectra out of which 12 belong to late-M dwarfs, 69 to L dwarfs, and 32 to T dwarfs. Sixty-eight of these spectra are presented for the first time. We measure strengths of the main absorption bands in the IRS spectra, namely H2O at 6.25 $\rm{\mu m}$, CH4 at 7.65 $\rm{\mu m}$, NH3 at 10.5 $\rm{\mu m}$, and silicates over 8–11 $\rm{\mu m}$. Water absorption is present in all spectra and strengthens with spectral type. The onset of methane and ammonia occurs at the L8 and T2.5 types, respectively, although ammonia can be detectable as early as T1.5. Silicate absorption sets in at spectral type L2, is on average the strongest in L4–L6 dwarfs, and disappears past L8. However, silicate absorption can also be absent from the spectra at any L subtype. We find a positive correlation between the silicate absorption strength and the excess (deviation from median) near-infrared colour at a given L subtype, which supports the idea that variations of silicate cloud thickness produce the observed colour scatter in L dwarfs. We also find that variable L3–L7 dwarfs are twice more likely to have above-average silicate absorption than non-variables. The ensemble of results solidifies the evidence for silicate condensate clouds in the atmospheres of L dwarfs, and for the first time observationally establishes their emergence and sedimentation between effective temperatures of ≈2000 and ≈1300 K, respectively.

A New Method for Measuring Infrared Band Strengths in H2O Ices: First Results for OCS, H2S, and SO2

Infrared (IR) band strengths are needed to extract accurate molecular abundances from astronomical observations of interstellar and solar system ices. However, laboratory measurements of such intensities often have required multiple assumptions about ice composition and thickness. Here we describe a method that circumvents most of the common assumptions and uncertainties in IR band-strength determinations. We have applied the method to measure IR band strengths of OCS, H2S, and SO2 in the absence and presence of H2O ice at 10 K, the first measurements of their type. Our results show for the first time that the presence of H2O makes little difference in IR intensities for these three sulfur-containing molecules’ strongest IR features. The immediate application will be to laboratory studies of low-temperature chemistry of interstellar and cometary ices.

Longitudinal Variation of H2O Ice Absorption on Miranda

Many tidally locked icy satellites in the outer solar system show leading/trailing hemispherical asymmetries in the strength of near-infrared (NIR) H2O ice absorption bands, in which the absorption bands are stronger on the leading hemisphere. This is often attributed to a combination of magnetospheric irradiation effects and impact gardening, which can modify grain size, expose fresh ice, and produce dark contaminating compounds that reduce the strength of absorption features. Previous research identified this leading/trailing asymmetry on the four largest classical Uranian satellites but did not find a clear leading/trailing asymmetry on Miranda, the smallest and innermost classical moon. We undertook an extensive observational campaign to investigate variations of the NIR spectral signature of H2O ice with longitude on Miranda’s northern hemisphere. We acquired 22 new spectra with the TripleSpec spectrograph on the ARC 3.5 m telescope and four new spectra with GNIRS on Gemini North. Our analysis also includes three unpublished and seven previously published spectra taken with SpeX on the 3 m IRTF. We confirm that Miranda has no substantial leading/trailing hemispherical asymmetry in the strength of its H2O ice absorption features. We additionally find evidence for an anti-Uranus/sub-Uranus asymmetry in the strength of the 1.5 μm H2O ice band that is not seen on the other Uranian satellites, suggesting that additional endogenic or exogenic processes influence the longitudinal distribution of H2O ice band strengths on Miranda.

Infrared Spectra and Intensities of Amorphous and Crystalline Allene

The infrared (IR) spectra, including spectral intensities, of solid hydrocarbons are of interest to astrochemists and astronomers for the relevance of these compounds to surface chemistry in the outer solar system and beyond. However, although the vibrational modes and IR peak positions of many such compounds have long been studied, much less attention has been paid to the IR intensities needed to quantify both astronomical observations and laboratory results. Here we present mid- and near-IR transmission spectra of a relatively little-studied solid hydrocarbon, allene (1,2-propadiene). Spectra of both amorphous and polycrystalline allene are shown for the first time along with optical constants, band strengths, and absorption coefficients. We also report a density and refractive index (670 nm) for each form of solid allene. A radiation-chemical experiment on allene’s formation is described, as are some applications and suggestions for future work.

Sakurai’s Object revisited: new laboratory data for carbonates and melilites suggest the carrier of 6.9-μm excess absorption is a carbonate

ABSTRACTWe present new room-temperature 1100–1800-cm−1 spectra of melilite silicates and 600–2000-cm−1 spectra of three randomly orientated fine-grained carbonates to determine the possible carrier(s) of a 6.9-μm absorption feature observed in a variety of dense astronomical environments, including young stellar objects and molecular clouds. We focus on the low-mass post-asymptotic giant branch star Sakurai’s Object, which has been forming substantial quantities of carbonaceous dust since an eruptive event in the 1990s. Large melilite grains cannot be responsible for the 6.9-μm absorption feature because the similarly shaped feature in the laboratory spectrum was produced by very low (0.1 per cent by mass) carbonate contamination, which was not detected at other wavelengths. Due to the high band strength of the 6.9-μm feature in carbonates, we conclude that carbonates carry the astronomical 6.9-μm feature. Replacement of melilite with carbonates in models of Sakurai’s Object improves fits to the 6–7-μm Spitzer spectra without significantly altering other conclusions of Bowey’s previous models except that there is no link between the feature and the abundance of melilite in meteorites. With magnesite (MgCO3), the abundance of 25-μm-sized SiC grains is increased by 10–50 per cent and better constrained. The mass of carbonate dust is similar to the mass of polycyclic aromatic hydrocarbon dust. Existing experiments suggest that carbonates are stable below 700 K; however, it is difficult to ascertain the applicability of these experiments to astronomical environments, and more studies are required.

Theoretical study of the helical conformers and ECD spectra of 8-aminoquinoline polymers

In this study, the helical conformers and absorption spectra of three types of 8-aminoquinoline oligoamides were studied. The stable conformers of these oligoamides connected with chiral β-pinene at their terminals were searched, and their dominant conformers and corresponding Boltzmann statistical weights were obtained. The excitation energy and oscillator strength of the dominant conformers were calculated, and the UV and electronic circular dichroism (ECD) spectra were also simulated. β-pinene can form delocalized π-bonds at the C-terminal, which results in a strong R band for CQn. Furthermore, the degree of polymerization also affected the strength of the absorption band for all the oligoamides.